Radio receiver system



July4,1944. J'. 1. DAVIS ETAL 2,353,111

RADIO RECEIVER SYSTEM Filed July 16, 1941 DIODE DETECTOR OUTPUT STAGES MonuLATon LF. AND Aumo AND csc* POWER SUPPLY Patented July 4, 1944 RADIO RECEIVER SYSTEM John I. Davis and Henry B. Saunders, Chicago,

Ill., assignors to Galvin Manufacturing Corporation, Chicago, Ill., a corporation of Illinois Application July 16, 1941, Serial No. 402,582

(Cl. Z50-20) 7 Claims.

This invention relates in general to radio receiver systems but more in particular to a radio receiver system which includes a radio receiver portion mounted on a mobile craft having a metal body, and a signal pick up portion which comprises solely the metallic body of the mobile craft.

During the entire history of use of radio receivers on mobile craft such as automobiles, trains. boats, and airplanes there has always been a problem to provide effective signal pick up means in rather limited mounting space, and provide an adequate signal strength at the receiver in the presence, normally, of considerable undesirable electrical interference. Although these problems have been present to a great or to a small degree in all such types of mobile craft, they have been most serious on automobiles, trucks, and the like where available mounting space for an antenna is normally at a minimum. In addition there are the factors of appearance, cost of the antenna or signal pick up means itself, and the cost of installation which at times have created problems.

Satisfactory signal pick up means, so far as the electrical characteristics are concerned, have been provided in the vertical jointed pole type antenna which is mounted on the outside of an automobile body, or at least extends outside and above the automobile body when in full operating position. However, some of the antenna of this type are costly in and of themselves, and in all cases the installation represents quite an item of cost. This often materially increases the cost of the entire radio receiver system installation. In addition to the problem of cost as discussed above, installation of such types requires cutting through the body of the automobile, and in many instances thel cut represents a permanent defacement. Furthermore, there has always been criticism of the outside antenna on automobiles from the standpoint of appearance.

Various parts of the automobile such as the bumper, and grille over theY front of the radiator have been insulated from the automobile body and employed as antenna, or signal pick up means, However, this installation, to insure that the part is permanently insulated from the body, is expensive, and in general the mass for original pick up purposes is limited.

It is an object of our invention to provide an improved radio receiver system for mobile craft.

Another object is to provide an improved and simplified signal pick up means for the complete radio receiver system on a mobile craft, which likewise provides a large signal pick up mass.

A still further object of our invention is to reduce material and labor costs in a radio receiver system, particularly as represented in the signal pick up means structure and the installation thereof on a mobile craft; and

Another object of our invention is to provide a radio receiver system for a mobile craft which has no objectionable appearing outside antenna or signal pick-up means.

A principal feature of our invention is the use of the metallic electrical conductor body of mobile craft for picking up signals to be fed to a radio receiver mounted on the mobile craft, and normally within the metallic body itself.

Other objects and features of our invention will be apparent from the following description taken with the drawing in which:

Fig. l is a schematic illustration of `a complete radio receiver system on a mobile craft.

Fig. '2 is a sectional view of a self contained unit employed in the radio receiver system of Fig. 1 for balancing out undesirable signal'impulses which are normally present on the metal-- lic body of a mobile craft so that such undesirable signals are not fed to the radio receiver of the complete system.

Fig. 3 is a fragmentary circuit diagram of a modification of the system of Fig. 1.

Fig. 4 is a fragmentary schematic illustration of a still further modication of the complete radio receiver system of Fig. 1.

In practicing our invention we provide a radio receiver system mounted on a mobile craft having a metal body which is utilized as the sole signal pick-up means for the radio receiver system. The radio receiver portion of the complete radio receiver system is electrically connected in at least one terminal point with said metal body and signals are fed from said body to the input circuit for the'radio receiver, and acted upon in the usual manner over the remainder of the receiver circuit. Normally the radio receiver portion is also electrically connected to said metal body to provide a ground connection at a point spaced from said terminal point, or points.

Fig. l illustrates diagrammatically the complete radio receiver system on a mobile craft represented, in the illustration, by an automobile having a metal body I0 serving as the antenna portion or signal pick-up means for the system. As illustrated, a lead-in wire Il is secured to themetal body I0 by suitable terminal means at a point'lZ. This point may be immediately above the windshield I3 on the body and adjacent the top for the automobile, or more conveniently, the lead-in wire II may be secured to the metal frame I4 for the windshield. This is accomplished by loosening a screw which secures the frame I4 to the metal body, and which screw is electrically common to the body. The lead-in I I can then be carried across or around the windshield to the receiver which is normally mounted below the cowl to the firewall or to the instrument panel of the automobile. If most convenlent, the lead-in may be carried below or alongside the usual mullion strip I1 at the dividing point of the windshield. The lead-in II extends through a small hole I8 which may be provided in the cowl I9 at the base of the mullion strip, or at any other convenient place and extends from there under the cowl I9 to a connection with the radio receiver. The electrical connection at the point I2 is substantially at the maximum vertical height within and on the automobile and hence normally is at a point of maximum signal strength. Although the connection and installation 'of the lead-in from the terminal point on the metal body has been described above in some detail, actually, it is understood that this is normally a relatively short lead,` and a very simple installation.

In the embodiment of Fig. 1 the lead-in is connected to the primary 2| of a preassembled inductance coil unit 22 whichincludes the `coil 2| and a second coil 23 inductively coupled thereto. Both coils 2| and 23 may be of the pancake" type and are insulatingly mounted within the unit. The'coil 2| is mounted in the 'slot 24 of an insulating rod 26 which is movably supported at each end in the shielding can 21 for the unit 22. The can provides the complete unit as a preassembly mounted normally within the radio receiver housing by securing it to the housing wall H by screws or the like 28. In this position the rod 26 extends beyond the housing wall and is available for rotation by a screw driver or the like at the head A, as will be explained. The coil 23 is fixedly mounted on an insulating backing 29.

The inductive coupling between the two coils 2| and 23 may be varied by slidably adjusting the metal gate 30 suitably mounted at an aperture 3| in a metal shielding wall 32 between the two coils. The gate 30 is suitably pressed against the wall 32 to maintain a good electrical connection therewith, and prevent rattling or looseness to set up disturbances within the shield. The adjustment of the gate is accomplished by a screw 33 supported within `the unit and available outside the housing H for the radio receiver at the head portion A for the screw which may be rotated by a screw driver or the like. In addition to the shielding gate 30 to change the inductive coupling between the coils 2| and 23, an electrostatic shield 34 of the type disclosed in Patent 2,047,159 issued July 7, 1936, is employed.

The coil 2| is in series connection with the primary 38 of the variable iron core inductance unit 31, whose secondary 38 is connected with the grid`39 of the first tube 4I in the first stage in the radio receiver. A trimmer condenser 42 acts to track the tuned circuit with the antenna portion of the radio receiver system, and an isolating condenser 43 is employed to prevent the A. V. C. circuit including the resistance 44 from grounding through the automobile battery 41. or through the secondary 38 of the tuning coil unit 31. The coil unit 31 is connected to ground at a point indicated by the reference character C. This may be a point on the chassis for the radio receiver which is in turn grounded to the housing H, and the housing H to the automobile body in the usual manner, or other suitable ground connections for the unit 31 may be employed.

In addition to desirable signal impulses picked up by the metallic body I0 and brought to the radio receiver as heretofore described, there are also present on the automobile body, or the metallic body of any other mobile craft of a similar nature, undesirable signal impulses representing high frequency interference originating primarily in the ignition system of the craft. With the battery 41 employed as the source of current for the ignition system of the mobile craft, as well as the A or filament current supply for the radio receiver, the undesirable signal impulses present on the metallic body are also common to the battery 41 circuit. Hence such signal impulses in the battery circuit are of substantially the same phase, and wave shape, as the undesirable signal impulses on the body, or signal pick up means. The undesirable signal impulses are carried over the lead 48 from the battery 41 to the coil 23, and with the coil coupling and phase relation between the coils 2| and 23 properly adjusted by the position of the gate 3|) and of the rod 25 and coil 2 I, the undesirable signal impulses carried to the coil 23 induce a current of opposite phase in the coil 2| to balance out the undesirable impulses carried to the coil 2| from the metallic body of the mobile craft. With the coils 2|and 23 of the flat pancake type any movement of the coil 2| as a result of movement of the rod 26 will change the phase relationship therebetween.

The A supply current is carried from the coil 23 through a conductor 49 to the lament 5I of tube 4|, and to the filaments of the remaining tubes in the radio receiver circuit as indicated in block diagram in Fig. 1.

A radio receiver circuit beyond the first R. F. tube 4| as illustrated in the representative system includes the modulator-oscillator-detector 52, an I. F. and diode detector 53, and audio and output tube stages represented diagrammatically by the reference character 54. A power supply 56 is provided for the entire circuit, and the signal impulses acted upon in the radio receiver circuit are reproduced at the speaker 51. The entire radio receiver is represented diagrammatically as `being housed within the metallic shielding housing H with the coil unit 22, as illustrated in Fig. 2, normally mounted within said housing as previously mentioned.

A modified embodiment of the invention is illustrated diagrammatically in Fig. 3 with the lead-in extending from a terminal point I2 electrically common to the metallic body I0, in the same manner as described with reference to Fig. 1. Likewise the balancing unit 22 is employed and connected in the same manner as previously described. The input circuit of the radio receiver includes a permeability tuning unit comprising a coil 5B and a variable iron core. In series connection with the single coil 58 to a pure resistance 59 connected to ground at a point C' corresponding to point C. A conductor 50 is connected intermediate the coil 56 and resistor 59. With this circuit signal voltage developed across the metal body ID from points I2 to C is inserted across the resistor 59, the resistance of which matches the resistance across the twopoints mentioned. l

Hence in the embodimentofl Fig.` 3, in =s1rbstantially the same Amanneras-.in the iembodiment of the invention of F.ig. 1, desirable `signal impulses represented substantially Aby the potential between the terminal point vand ground on themetal Vbody -lll'are fed through the lead-in lvl to the input circuit of, the radio receiver.- The radio receiver'is tuned to the desired frequency by means of the unit including .the coil 58, and other similar units if. required, in 'the usual manner. v

In'practicing our invention We have-also fou-nd that desirable signal pick up is obtained Witha pair of lead-in wires vfrom the metal car body-to an aperiodic type of input circuit in tlreradio receiver portion -ofthe complete receiver system.` This embodiment is illustrated in Fig. 4 with the lead-in Il connected to one side ofthe low impedance `primary 6| of -anfinput coil v62 in the receiver. A Vsecond lead 63 is connected -to the other side of the coil 6| and carried .through :a shielded covering .64 to a terminal point 66 'preferably at about the same level in the mobile craft as the radio receiver itself, and consequently normally at some poi-nt on the cowl 'I9 :of the craft or automobile. Thev impedance nf the metal body I of an automobile, .is normally low and hence `the impedance of the coil 62 is low, with `a coil of only three-to lsix turns normally being satisfactory in the input circuit. The secondary 6.8 of the coil 62 .isconnected to the grid 39 of the first coil as previously described. In this embodiment for purposes 4ofillustration a variable condenser 69 is shown rather .than the permeability tuned unit 31 of the previously rdescribed embodiments. It is understood .that permeability tuning, or capacity tuning may be em; ployed in any of the embodiments of the invention. The low vside of thecoil 68 is grounded at C", and a Ypadder condenser 'H is employed to track the antenna circuit with the remainder of the tuned circuit. The signal pick up of the embodiment of Fig. 4 is represented by the potential difference between the terminal points I2 and 66 on the metal body.

It is understood therefore, from the above description, that our invention provides a radio receiver system which does not require an antenna independent of the mobile craft upon which the radio receiver system is mounted, but

rather utilizes the metal body itself of such mobile craft. As a result, signal pick up means is immedaitely available merely by the connection of a Wire from the radio receiver to the metal body of the mobile craft. This eliminates costly antenna equipment and costly installation. In addition, there is no outside apparatus detracting from the appearance of the mobile craft, and no defacement of the craft is required in order to provide signal pick up means.

Although the invention has been illustrated and described in its preferred embodiments it is understood that it is not limited thereby, and is limited only by the scope of the appended claims.

We claim:

1. A radio receiver system for an automobile including in combination a metal body for said automobile acting to pick up desirable and undesirable signal impulses and serving as the antenna for the radio receiver system, a radio receiver mounted on the automobile body and grounded thereto, said radio receiver including an input circuit, a lead-in conductor in series electrical connection With said metal automobile body and with said input circuit, a source of current supply for'said radio receiver'. which is also the current supply for the automobile,` andy conducto'r Imeans connecting said current supply andsaid radio receiver having a portion 'thereof inductively coupled to a portion of said leadin conductor.

2. In .a radio'receiver 'system the combination with a radio receiverfof a `metal body of a mobile craft comprising the sole antennaior `tiierzidio receiver fand with said radio receiver carried 'on said mobile .craftrand electrically grounded thereto, tuning'means for'said radio receiver, an inductancecoil in series connection with said tuning means, conductor means electrically connecting said metal vbody and `said inductance coil to carry desirable and undesirable signal impulses' to said inductancel coil, a current supply Vsourceelectrically commonto said mobile craft and to said radio receiver forsup'plying electric ycurrent to both said craft and said receiver, an linductance coil coupled to said lirst mentioned ind'uctancecoi'l and electrically connected to said "current supply source and to said radio receiver, with lsaid `second mentioned Ainductance coil receivingr undesirable signalv impulsesv from said current supply source `of the same general nature as thosev Acarried from said metal bodyto said rst mentioned .indufctance coil, and with said vundesirable signal. impulses being balancedout in said coupled inductance coils and said desirablesignalimpulses being carried from said iirstmentioned =coil to said radio receiver.

3. In a radio receiver system for a mobile craft, the combination with ya radio receiver 'carried on said mobile craft and electrically grounded thereto and having an .input circuit, of a metal body for said mobile craft which comprises the sole 1antenna for the radio receiver and which picks up able signal impulses electrically common thereto, and unit means for substantially eliminating the undesirable signal impulses but feeding the desirable impulses to said radio receiver, said means including a shielding housing, a pair of inductance coils mounted Within said housing with one of said coils being xedly mounted and means for means electrically connecting said one coil and said current 4. A self contained unit for use in a radio receiver system having an antenna portion and a receiver portion to remove undesirable signal impulsesy from the line carrying desirable signal impulses and undesirable signal impulses from the antenna portion to the receiver portion of said mounted in said can, and means for rotatably mounting the other of said coils including an insulating rod rotatably mounted in said can and extending in a direction parallel to the plane of said fixed coilf'havlng a 'slit' at one end carrying said' other coil insaid slit, with saidv rod being rotatable outside said can to move said coil thereon into and out of parallel relation with said fixed coil.

5. In a radio receiver system for amobile craft, the combination with a radio receivercarried `on said mobile craft, of a metal body for said mobile craft which comprises the sole antenna for the radio receiver and which picks up thereon desirable and undesirable signal impulses, said radio receiver being electrically grounded to said metal body, an electric current supply for both said mobile craft and said radio receiver having undesirable signal impulses electrically common thereto, and means connected to the metal body and to the radio receiver for substantially eliminating between the metal body and receiver the undesirable signal impulses but carrying the desirable signal impulses to the radio receiver, said means including a pair of coupled inductance coils with one of said coils electrically connected to said metal body and the other of said coils electrically connected to said current supply. and with each of said coils electrically connected to a different part of the radio receiver.

6. In a radio receiver system for a mobile craft having a metal body and having an electrical system thereon including a source of electric current, the combination with a radio receiver for said system, of the metal body of the mobile craft comprising the sole signal pick up means for the radio receiver and picking up desirable signals and undesirable signals, said radio receiver being electrically grounded to said metal body and having an input circuit including a variable iron core inductance coil and a resistance in series connection therewith, and means for carrying signal impulses from said metal body to said input circuit including a conductor electrically connected to said input circuit intermediate said resistance-and said coil, a lead-in extending from a point ofA electrical connection with said metal body, and a coil unit intermediate said conductor and said lead-in including a first coil in series connection with said lead-inv and said conductor, and a second coil coupled to said iirst coil of said unit and in serieselectrical connection with said radio receiver and with said source of electric current ior said mobile craft which is also the source of electric current for said radio receiver.

7. In a radio receiver system for a mobile craft having a metal body and having an electrical system thereon including a source of electric current, the combination with a radio receiver for said system of the metal body of the mobile craft comprising the sole signal pick-up means for the radio receiver and picking up desirable signals and undesirable signals, said radio receiver being electrically grounded to said'metal body and having an input circuit including a 'variable inductance unit having a pair of series connected coupled coils, a ground connection intermediate said pair of coils, means for carrying signal impulses from said metal body to said input circuit including a conductor electrically connected to said input circuit in series with one of said coupled coils,A a lead-in extending from a point of electrical connection with said metal body, a coil unit intermediate said conductor and said lead-in including a first coil in series connection with said lead-in and said conductor, and a second coil coupled to said first coil of said coil unit and in series electrical connection with said radioreceiver and with said source vof electric current for said mobile craft which is also the source of electric current for said radio receiver.

JOHN I. DAVIS. HENRY B. SAUNDERS. 

